The present invention pertains to a solid-state image sensor device of a type which may be used to advantage in a video camera or the like.
A conventional image sensor device of the type to which the present invention relates is shown in block diagram form in FIG. 1. In this device, a sensor array 10 is provided having a large number of pixels (picture elements) arranged in rows and columns. To produce an electronic signal representing a sensed image, the sensor array 10 is exposed to the desired image. Following exposure, a vertical shift register 12 activates its output lines in sequence. For each activated output line from the vertical shift register 12, outputs from the corresponding row of pixels are placed on output lines 16. While the output from the vertical shift register 12 remains in the active state, a horizontal shift register 14 is activated to shift a pulse along its output lines 17, thereby to activate output transistors 15 in sequence. This places the output signal in sequence upon signal output lines 18. The signal output lines 18 are applied to an amplifier where they are summed and a composite output signal produced.
The conventional image sensor of FIG. 1 suffers from a major drawback, namely, switching transients caused by signal transitions on the output line 17 of the horizontal shift register 14 induce noise in the signal output lines 18. Because this noise occurs at the fixed rate of the horizontal shift register pulses, the noise is termed "fixed-pattern" noise.
It is a specific object of the present invention to provide an image sensor which the amount of fixed-pattern noise is remarkably reduced.
Furthermore, it is an object of the present invention to provide such an image sensor in which the fixed-pattern noise is reduced without requiring complex and costly circuitry.